Morbidity and mortality associated with severe infections caused by Staphylococcus aureus present a staggering burden on the healthcare in the United States. The increasing antibiotic resistance of S. aureus limits effectiveness of available antibiotic therapies. The long-term goal of this project is to identify novel approaches that could be used to decrease severity and improve the outcome of staphylococcal infections. Staphylococcal pore-forming toxins, such as alpha-toxin and Panton-Valentine leukocidin, contribute to the pathogenesis of staphylococcal infections by triggering the release of pro-inflammatory mediators and inducing death in susceptible cells. During our prior studies we found that type I interferons (IFN-alpha and IFN-beta) potently decrease pro-inflammatory responses and cell death triggered by staphylococcal alpha-toxin. Our preliminary data also suggest that type I interferons prevent formation of alpha-toxin pores via induction of), an interferon-stimulated gene involved in plasma membrane lipid turnover. Building on these novel findings, we hypothesize that type I interferon-induced protection from alpha-toxin benefits the host during staphylococcal infections. To test this hypothesis, we plan to determine whether type I interferon-induced protection from alpha-toxin decreases severity and improves the outcome of staphylococcal infection (Aim 1). We will evaluate the effects of type I interferons on bacterial clearance, tissue injury and induction of pro-inflammatory cytokines (IL-1-beta, IL-6, TNF-alpha) and chemokines (MIP-2 and KC) during experimental staphylococcal infection in a mouse model. Furthermore, we propose to determine the role of PLSCR1, as the most promising candidate gene, in interferon-induced protection from alpha-toxin (Aim 2). Using RNA-interference approach and PLSCR1-knockout mice, we will determine whether PLSCR1 is necessary and/or sufficient for type I interferon-induced protection from alpha-toxin. These experiments should provide novel mechanistic insights into the roles of type I interferons in the regulation of host interactions with S. aureus. The results of these studies should also help us to evaluate whether targeting type I interferons or PLSCR1 has a therapeutic potential for treatment of staphylococcal infections. PUBLIC HEALTH RELEVANCE: The increasing antibiotic resistance of S. aureus limits effectiveness of available antibiotic therapies for treatment of staphylococcal infections, which are linked to approximately 12,000 patient deaths per year in the United States. We found that type I interferons limit inflammatory responses and cell death triggered by alpha-toxin, a major virulence factor of S. aureus. We propose to evaluate whether interferon-induced protection from alpha-toxin benefits the host and has a therapeutic potential for treatment of staphylococcal infections.